doc: add changelog

Author: Jui-Nan Lin

docs/changes/2.x/2.0.0.md

@@ -6,6 +6,7 @@
 
 - IOFactory : Added extractVariables method to extract variables from a document [@sibalonat](https://github.com/sibalonat) in [#2515](https://github.com/PHPOffice/PHPWord/pull/2515)
 - PDF Writer : Documented how to specify a PDF renderer, when working with the PDF writer, as well as the three available choices by [@settermjd](https://github.com/settermjd) in [#2642](https://github.com/PHPOffice/PHPWord/pull/2642)
+- HTML Parser : Added support for rowspan in add HTML [#1643](https://github.com/PHPOffice/PHPWord/issues/1643)
 
 ### Bug fixes